Method of making tempered blades



/rozgbout I 0. NAPIER.'4

METHOD 0F MAKING TEMPERED BLADES. 'APPLICATION FILED DEC. 9, 1918.l v 1,333,767. Patented Mar.16,1920.

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CHARLES NAPIER, .0E srnrireEIELD, MASSACHUSETTS, AssIeNon To NAPIER sAW woExs me., E

cnUsE'rTs.

, To all 'whom t may concern: I

-. Be it known that I, CHARLES NAPIER, aj

citizen of the United/ States of' Amer1ca,

and resident of Springfield, in the county of Hampden and 'State' of Massachusetts, have invented new and useful Improvements in Methods of vMaking ATempered Blades, of which the following is a specication.

. tion comprises aneimproved method or art of making a blade or -tool having new and v valuable characteristics.

In my Letters Patent No.` 1,221,57 6, dated April v3, 1917, Ihave explained a machine for vuniformly tempering saw-blades, and in my Letters Patent No. 1,265,944,:dated May 14, 191.8, I have explained a method of heat` treating such blades adapted be carried out with the aid of such ra machine, the product of the later' atent being a uniformly tem ered blade ,with aJmealed or soft ends use ul as a' hack-saw andfor other purposes.

Such blades are first hardened and then drawftempered `throughout their -middles and` edges to the degree of hardness or-temper heretofore customary for-'such'4 blades. This customary degree of. temper is such," the instance of, lthe hack-saw, bandsaw' and other such blades of prior knowledge," as to provide a moderately -flexible and j resilient blade. uniformly hard enough 'to enable any ofits. edges toserve 'as la metalcutting` edge, the' iinished blade proper,`i nl cluding the edge, `being thus. characterized.

by av uniform crystalline structure with' a low elastic limit, andtherefore being brittle cutting) edge is impaired at ally by wear.'

against Sharp-bendingor sudden blows. In the best practice. of which .I am aware, l. have 'collected Astatistics showing that more `than 42 per eentuln ofhack-saw blades are broken in use before the usefulness of the Such eakage represents' al loss of'V value l Specieation of Letters Patent. lApplication led ecember-S, 1918. Serial No. 265,836.

SPRINGFIELD," MASSACHUSETTS, A CORPORATION OF MASSA` METHOD O'F MAKING TEMPERED BLADES.

Patented Maf. 16, 1920.

of a still higher gure if breakages after 5o` a partial use of thev tool should be lncluded.

A rincipal object. of the present invention 1s to avoid such losses of value by the provision of an efficient and practical way of making a bladel having a cuttingl edge of greater hardness than has heretofore been practicable and a body which will not break under the ordinary strains of use.

Available tool-steels have heretofore necessitated for such uses a compromise between resilient flexibility and hardness, a

high elastic limit being attained by'drawtempering with .any available material only upon treatment resulting in yreducing the hardness of the metal below an attainable, and for metal-cutting purposes, the most useful value or degree. .For` instance, it is my experience that a' glass-hard state, attained by rst heatingto a high critical temperature and thenchilling or quenching, is ,most useful for the edges, points or Ateeth of a metal-cutting saw, knife, or 'mill-` ing cutter in respect ato. its attack upon the material; vbut it is also myjexperience that this state is impracticable for such an instrument as a saw-blade, because: the desirable rquality of 'extreme hardness is aecompanied by such brittleness and susce tibility to breakage in `use as' to limit'un uly the life ofthe tool.` 1 v It has, therefore been customary heretofore ,to sacrifice the quality of maximum hardness Ain favor of an 1ncreased-sprmg1 pered by subjection to a moderate, uniform heating after hardenin so as to stand "inod-` erate bending'without reakage, idespitethe fact that. this treatment reduces the extreme hardness ofthe cutting edge which it would."v

have' been'advantageous to retain, if `.there were any way to keepv it compatible with securing toughness and resilience. When I have discovered"`that a cutting edge 'ef such a tool fas a -knifefband-saw orhacksaw blade .may be kept at a point at/ or near maximum hardness, thereby to produce a cutting 'tool' of 'heretofore unlmown durability and eiiiciency, if the hard edges or portions are supported by intimate'and .paratus for practising the method;

integral contact with portions of the body of the blade gradually decreasing in hardy ness and increasing resilience orsoft-V ness within thehard points or edges. For

treated; and

' instance, points or edge portions which have vbeen heated above the hardening reaction Y1o point, quenched or chilled, [and if desired slightly draw-tempered to an extent not ref ducing the desired hardness for cutting at .v

a low heat, about 350 F. for instance, for

tool-steels of usual composition] may sup- 15 I the same `metal which has'been first har-v ported upon' integral basesl or a backingy of dened and theny drawn, as 'the edge is receded from, at temperatures varying with the extent of recession from the hard points or' edgesfrom about V350 to about 800 F., or such other temperature as will leave the article ina springy resilient state. 'Sucha spring tem r is a highly desirable quality of .the bla e pro er of suchan article, but it is not compati le with suicient hardness for metal cutting, and is as detrimental at the ultimate cuttingedge or point as it is valuable in the bod of the tool. i

l do ngt hereinc aim such a eblade or tool as 'an article ofv manufacture, that part of my invention being the subject of a divisional application Serial No.. 274,006, filed Jan.j30,^1919, for separate Letters Patenti' 'Y have devised and will hereinafter descrlbe a -method or. art of r apid1y,funi

formly, and if desired, continuously treat.v ing such articles 'soas to provide them withhardcutting points or'edges and with gradf u ally and increasingly softer and more flexibly resllient supports for the point or edge within the point or edge, and with uniform' spring-tempered bodies integral' with and bearingsuch support and edge. As an article, of manufacture, the resulting product retains'the cutting quality of hardteeth or edges against long Wear, and resists breakage remarkably. 1I shall herein describe as an instance of the genus of new articles -characterized by my inventiona hack-saw blade, and I shallalso herein describe asv one instance only of the method'of heattreating such. a blade also constituting a part of Y'my-invention, steps Aspecifically a plicable to this particular article, but applR# cable without change except of apparatus or degree `to the treatment of other specific 'articles included among the newl genus of articles comprising my invention.

VIn' the accompanying drawings,

Figure lis a diagramelevatlonfof atypical specimen of the article of manufacture; wig; `ig. 2l is an enlarged detail of the area -2-l-2 dfFgl-: .Q n

Fig. 3 is a diagram section online of 2- illustrating graphically therelative 65l hardness of 'the metal at different parts;

Fig. v4 is Aadlagram plan of preferred ap- Fig. '5 is van enlargedfdetail Vdiagram in .plan showing relationships vof temperatures and' previous conditions-of .thejmetal'being "metal'is that in which the blade 10 is uniformly spring-tempered toa flexible. resilience with a high elastic limit throughout the '80 region 13 comprising the greater part of the body or blade; .and in. which the points,

faces and cutting edges 15 of the teeth are of the maximum'hardness compatible with enough' tensile coherence to prevent chip- 85 i pingor shivering. At theultimate edges and'point s, t lii s maybe the/maximum crystallin'e hardness which their metal is capable 1of assuming,such as will follow heating above?y the critical temperature [1200o to 90 -1400 F. or higher for toolv steels of. commen cial composition] and immediate quenching at. temperatures lat or below 850" lflany considerable depth ofthe teeth or edges 'of the saw is\"in Such a crystalline 95 state, breakage under use .is inevitable. For` instance, if a Wholetoothcomprising the points and edges and faces 15 and the base 1 'or root 16 is in this state, vbreakage of that tooth under lateral strain or a sharp blow or bending ofthe blade at a moderate anglais to be expected. If the re 'on 14 adjoining the teeth'is glass hard,.suc a breakage may involve two-or more teeth. But if only the faces and edges and points are of a crystal- 'line hardness, if the roots or bases 16 are hard but tough, and if' the region 14 back .of the roots 16 partakes of the qualities of resilience and flexibility, breakages -of teeth do not occur. Desirably, then, ,the hard points and faces 15 and the spring-tempered'body 1 3 arel separated .by a vregion 14 partaking of the' qualities of the hard partsat these parts, and of the qualityof the springy part. at the ,'uncture at line 'a of the blade, which' may 115 near the toothed or cuttinged e. Ihave found that the best results for e ciency and durability are attained when the region 13 uniformly spring-tempered vand vwhen the region 14 increases in hardness fromtuni'- 120 formity with the temper of region 13 from the line a toward the toothed .'edg'e. As shown graphically Fig. 3, .a curve w whose ordinates represent hardness at abscissae successively approaching the edge rises toa maximum at t e ed e.k f

Preferably the;l blade o .the kind provided. with perforations '11 at each` end and Lesage? '.with soft or Iannealed rregions 12v at the i' 12, 12, and the edge'regon 14 has first een.

neighborhood of the perforations, res ond entA No. 1,265,944; The blade proper, com-l prising the regions 13` between the re ions subjected to heating above a critical temperature dependent on the material [for instage.

stance to the cherry-red hardening temperature for tool steels of usual carbon contents adapted to take a hardening reaction at the cherry-red temperature] has been thereafter subjected to sudden cooling, as in an oil bath; and the region 13 only has been tempered by subjection to a temperature in a neighborhood of 800 F., more or less, in accordance with the reaction of the particular metal under treatment at the hardening The region 14`and the faces, edges and points 15 have been subjected to steps first hardening these reg-ions uniformly; then heating them above the temperature for hardening reaction; then chilling or quenching;

and then"drawing the temper of the region 14 and the bases of the teeth, points or edges by regulated causation of temperatures decreasing toward the edges or'r points and act-` ing during a predetermined time only, 'the effect being' to spring-temper the part of the strip 'orregion 14 at its juncture with the spring-tempered blade, and to leave unaffected the condition attained at the edges or. points when the edge containing thenrwas quenched or chilled. Preferably the quenching of the edgejstrip 14 was so conducted as to occur at a regulated minimum tempera ture. consonant with drawing the temper of .the 'inner` side of the strip and the inner parts of the `metal' blade during maintenance of this temperature at the chilled faces, edges and points. j

These qualities of the product will best be understood by explanation of a specific preferred instance of the steps taken in mak- 1ng on a commercial scale articles of the kind referred to. j

Referringv now to Figs. 4, 5V and 6, the process is preferably practised continuously by subjection of a series of the articles to vbe treated successively during predetermined times to th'e different stages of treatment. A convenient way to do this is to provide for joining the articles end to end in a chain and to move them forward, for instance by' such means as disclosed in my said Letters Patent No. 1,221,576, dated April 3, 1917,--at a constant rate` (either intermittently by short steps or continuously)` past heating, quenching, reheating, tempering, cooling andwashing devices suitable to the articui lar result desired; but it will be un erstood that yanyfdesired means for subjecting the articles in succession to the described stages of treatment may be em loyed.

The individual artic es 10 first' pass Vthrough a. gas-heated? munie-furnace 20 in which the articles 10 'and their connectors 9 are heated uniformly. `Preferably the articles, if for saws, are of steel of one of the following typical analyses:

y In either case a temperature at Inutile 20 of from 1350"- to 1400 F. is satisfactory,

land this is readily attained during progress of the saws at about 14 feet a minute through a hot passage aboutthree feet long.

From the mulle the saws pass to a quenching tank 30 in which a suitable liquid,.such as van oil or emulsion at about F. chills the saws to a uniform glass-hard state, except at the ends, which are prevented from rapid cooling by the mass of holders 9, and remain soft.

The saws now pass into a heater 40 in which the blades are heated. to about 800 to 850, to draw the temper of the region 13 to al spring temper, and to heat the edge" strip 14, 15, again to a red heat at 14000 or more. Preferably a metal block 41 channeled at 42 to receive all of the saw-blades except' the strip 414, 15, is positioned to rea block 41 and a refractory screen 43` suported on a base 44, and adjustable gaslasts 45 playing downward upon the exposed edge strips 14 and the block 41. By

. proper' regulation of the length and massof the block 41, the intensity, temperature and vnumber ofthe gas-blasts 45, no diiculty is found in maintainingthe relativetemperatures of the regionsr13 and 14 of thel saws at exit fromY the heater 40 at'the desired figures, which are near or slightly in excess of 800 and 14.00 F. 'respectively foi` are body -andedge strip, asiidicated in Fig. 3.v .The block 41 may be about ten inches long for an article-chain speed ofll feet a-minute.

Saws which were cool and glass-hard before entering heater 40 thus leave it differentially l heated to degrees adapted td cool slowly. to

a spring temper and to chill to hardness respectively at the regions 13 and 14.

The heated blades are now subjected to treatment at a 'bath50 adapted to resist rapid cooling of the 'on 13; and rst to quench or chill the strip 14 and the faces,

distance, represen edges and points at lthe edge 15, and thereafter to permit the residual heat of the body 13 and strip 14 to eiect a predetermined vdrawing of the -temper of the strip 11h A and strip M, except the edges and points," falls to or near to the temperature' ofthis bath. The verhotstrip 14, and especially I the ,.edges, faces and points 15 fall to this temperature so rapidly as to harden the cutting edges to the desired maximum degree; Y buttlie'regioni13 does not harden. I have discovered that there is a suiiiciently rapid drop oftemperature at the points andedges from red heat toward. the temperature of@ theliotvoilbathtoca A out this reaction; that in a bathV as descri at or near-3509Y the' tempering-reaction at Darts which have been heated only to ampderate temperature near 800` continues to the improvement of resilience and iiexibility, and that a spring temper is under these conditions commum- 14 to adegreedependingr 0n the time the conditions remain as indicated in bath 50. 1 Nthe-article to attain the qualitiesfof to ness andflexibility', re-hardenin'g vregion only of the article, and

portion of said edge.regonj adjoining the cated progressively 'from region13 intolstrip ascribe the observed phenomena to the ac tion' in bath 50 after the quenching of the Yedge 14 pf the residualheat of the greater mass of metal, i; e., ofthe body 13 of "theJv blades, since I vii'ndthe distribution of hard- A Y tance along the running chain [-andhen'ce on nessinl the' striph14 to depend on the ds the time] during which the liot stream Vin bath is allowed to act. The'depth inward `from edges and points 15 at which the metal is at hardness variesin- Y1- `Y the shallowenwill be the hardest verselyasthis distance, so 'that Vthe longer the the time taken at this The 'Y times Vinvolved are relatively e of about two secondsin the 'hot bath sncient for hackssa'ws less Il ch .ckt j .E Y

Piltsi Short imm Vapproi'riinatel to its own temperature.`

. atl

temperin a springV temper,

:The-effect `of the apparatus be readily varied by adjusting t e-lcngth'Y of the stage 50. Conveniently thisis done by providing means for reducing the temperature of the saws in 'such a manner as to limit the length of the reaction dueto bath 50. The appa` Vi'atus shown. provides a cold bath 60 adjustable toward and away from thenozzle 51 so as to limit the time of immersion inthe hot oil to produce the desired effect. Bath v60 may comprise a screen 61 to stop the hot oil stream, and maycontain anoil oreinul-- sion at 100 F. or less. Y

Bath 60-is long enough to reduce the saws ter passing ath, 60 the saws may pass through any desired form offwash-tank coni taining a hot alkaline washing ilution,

after which the saws are se arated from the chain, and packaged for e.

[While I have mentioned a chain of hack- Asaw blades, it will be understood vthat the method or art andthe apparatus mentioned is applicable Vwithout change to treatment of o er elongate articles to. produce the characteristic .qualities v above described.

The treatment is adapted without change to band-saws, for instance, and produces for this use a band characterized by resilience adapted to long lifeV under the repeated bending to which such saws are subjected,

and byahardness at the teeth adapting the band saws to metal to a degree heretofore unknown.l :Other articles, suchas knife-blades, circular saws andV cutters included. among. the new genus-may be treated by the described with suitable changes in the'apparatus w 'ch be obvious to' persons infomed 'by this disclosure. I do notherein claim the apparatus mentioned which forms the subject of my application No. 269,598, filed' J auf' claimisz- Y. Y 1L The art of treating hardened metallic articles comp h treatingyhe ing tempering the body of body of the article t increase its .flexibility and toughness -2. 'Th'e.art of the body ofthe blade to ardening'an edge of the blade, and draw-tempering theY region between edge metallic blades comand body to a state of hard-l ness' intermediate between that of the edge temper, then Yhardening an edge of' treatingimetallic blades comand then drawing y of the blade to aassays? blade, and draw-tempering the edge regionv between edge and body to a state of hardness exceedin that of the body andgradually varying 'rom that of the body to that of the edge, the edge remaining hard.

5. The art of treating metallic blades comprising first hardening and then drawing the temper of the body of theblade to a spring temper, then hardening an edge of the blade, and then draw-tempering a por-- tion of' the edge region between edge and body to a state of hardness gradually varyedge, the edge remaining hard.

ing from that of the body to that of the 6. The art of treatingbmetallic blades co l prising tempering the lade and hardening the edge region by subjection respectively to suitable diii'erent temperatures Iand thereafter lowering the temperatures respectively of these parts sufficiently to chill the edge region while maintaining a state of temperi heat in the body. n?. The art of treating metallic blades com# prising tempering the blade and hardening the edge region by subjection respectively to suitable different temperatures and thereafterioweri ng the-temperatures respectively of these parts suiiciently to chill the edgeregion while maintaining a state of tempering heat in the lbody during sufficient time to affect the temper of the edge region at its juncture with the body. A

8. The art of treating metallic blades comprising tempering the blade and hardening.

the edge region by subjection respectively to suitable diii'erent temperatures and thereafter lowering the temperatures respectively l of these parts suliciently to chill the edge hardening reaction, and then subjecting the region while maintaining a state of tempering heat in the bodyfor a predetermined time during which the .temper of the edge region is drawn progressively toward the edge, and thereafter cooling the blade to stop 4further changes of temper. "i

9. The art of treating metallic blades comprising hardening the blade, subjecting the body of the blade to heating to a degree suf- Iicient to temper to a resilient and .iexible state, concomitantly heating the edge region 'of the blade to a temperature markedly higher than the and suiiicient for the whole blade to a bath at a temperature sufiiciently low to quenchor harden the edge and edge-region, and suiliciently high not'to quench, harden, or check thev spring-tempered body.

10.v The art of treatin steel blades compising hardening the b ade subjecting the yofmthgblade to heating to a temperapered body, during a ture of the order of 800 F., concomitantly subjecting the edge and edge-region 'of the blade to heating body of the blade to heating to a tempera.-

ture of the order of 800 F., coneomitantli7 subjecting the edge and edge-region of the blade to heating tov a temperaturey of the order of 1400 Fr., and subjecting the blades whilefso hea-ted' to the action of a'bath at a temperature of the order of 350 F. for a predetermined time.

12; The art of treating steel blades comprising hardening the blade, subjecting the body of the blade to heating to a temperature of the order of 800 F., concomitantly subjecting the edge and edge-region of the blade Vto heating to a temperature of the order of 1400 F., and subjecting the blades while so heated to the action of a bath at a ltemperature of the order of.350 F. for a predetermined time, and' at' the expiry of vsaid time lowering the temperature of the blades toL stop the progressive drawing of the temper ofl the edge-region toward` the condition of the body of the blade attained during the preceding step.

13. The art of treating metallicblade comprising hardening the blade, subjecting the body of the blade. to heating toa 'degree sufficient to temper toia resilient and flexible state, concomitantly heating the edgel region of the blade to a temperature markedly higher than the body and suiiicient for the hardening reaction, and then subjecting the whole blade to a bath at a temperature sufficiently low to quench or harden the edge and edge-region, andsuiliciently high not to quench, harden, or check the spring-tempredetermlned time, and thereafter subjectmg the blade to a bath at a temperature adapted to check further changes of the condition of the metal.

14.'The art of treating metallic blades comprising subjecting the blades progres.-

sively during predetermined, times toy the stages' of treatment, irst, heating above the temperature 'for hardening reaction; then .quenching to harden throughout; then heating the bodies ofthe lblades uniformly to a lesser heat adapted to draw the temper'to a springy state and subjecting the edge-regions of the blades to a temperature-above the temperature for' hardeningl reaction;

. then subjecting the blades to a hot bath Aat a temperature suiciently low to harden the edges and edge-region, whereby to maintain the tempering heat of the body of the blades; then subjecting the blades t0 a bath at a temperature checkin 'further change in the condition of the bla es.' v

ipso The Steps inthe-art f treating metallic articles by heat comprising-l heating Kart of the articleto the temperature lfor ardening reaction; tconcolnitantly yheating v5 another part ofthe article to aJlesser degree appropriate to a tough and flexible temper,

and subjectin the article. whileinfsaid state di erent temperatures for a pre-IV of locally Jsively changed' at andfrom thel juncturel of said hardened parts with theparts' heated to the lesser degree during maintenance in said bath-A@ A 16; Ill a.'

method .heat-treating 'saw-V 'i blades, vthe steps-comprising hardening-the' blades, then subjecting the edge-regionvcon-i tainingthe teeth and-V the body ofthe bla-de;

of the-saw respectively to local heating to a highY temperature forhardening and a lower l 'temperature for spring-tempering, quenchV rature of ingthe'blades in a 'bath ata-tem J the order oQ350", lwhereby to region; and their maintaining the time during which thev temper Lof the'ha-lA .17. The of treating metallic blades determined time tol V:t1- bath heated to a point adapted to conserve the temperature'offthe. cooler parts of the article and quench'or-Y' chill to harden the hotter parts, whereby the Y 'temper of thehardcned parts is progres- A de ned when quenched to a d bythe extent of said bath, andA the rate of l grecs of' heat, and

. rden the faces,points-and edges of the teeth andthe is aifected. i

mined rate respectively through means for f comprising moving-the blades'at apredeteifl locally heating the blades to'diierent pre-Y determined temperatures andthrough a predetermined extent of a heatedbath adapted to quench the hotter parts, andjto permit the cooler parts to remain at 'a heat reacting dul'ing'the-time of assage .in said bath to draw the'temper .o 4adjoining arts haretermined motion of the blade.

v1a in a .method of tfeat'in metalli#I blades, theste'ps locally heating a lade running at al predetermined rate to different deimmediately subjecting the heated running blade to the action rof a in the blade. A 19. lThe method of heat-treating metallic blades .comprising locally heating a blade ;bath adapted substantially to conserve the previously attained' tem crature of one part -of themetafI and toffa ect the hardness or temperof the metal differently at another Y previously heated part, the time elapsing between said steps bein .insuliiciet substan-Y tially to change `the dlstributionof the heatf moving at a predetermined rate to predetermined different temperatures and then subjecting .thelocally heated blade to the action of a stream vof ahot.quencb'in'gagent following Signed by meat Springfield, Massachusetts, this 5th day of December, 1918.V

" f .CHARLESNAPIER`- the blade for a predeterlmned disw tance of travel at said rate. 

